The diagnosis of physiological conditions such as cancer, infectious disease and prenatal disorders, is of paramount importance to the prevention, monitoring and treatment of such diseases. Typically, a biological specimen from a patient is used for analysis; identifying the presence of particular characteristic features of the disease indicates the presence or predisposition towards the disease. Biological sample analysis in its most traditional sense is performed by microscopic examination which, depending on the magnification, can be used to visualize the presence of abnormal numbers or types (e.g., cytology) of cells, organelles, organisms or biological markers.
Automated microscopic analysis systems have been developed to analyze specimens quickly and have the advantage of accuracy over manual analysis in which technicians may experience fatigue over time leading to inaccurate reading of the sample (see, e.g., the ACIS system, Chromavision, San Juan Capistrano, Calif.). Typically, samples on a slide are loaded onto the microscope, the microscope objective or lens focuses on a particular area of the sample, and the sample is scanned for particular features or objects of interest. To achieve an accurate image of the sample or particular features or objects in the sample, the sample must be focused. However, for various reasons present focusing methods and systems often have difficulty or require extended amounts of time to attain an optimal image focus. Improvement in image quality and the speed with which images are focused in microscopic systems will lead to improvements in sensitivity, speed, and accuracy of sample analysis and the diagnosis of disease by such systems. The invention mitigates this problem and provides related advantages.